Fruit Expert Tries to Predict Impact of Climate Change

Whether or not he believes in climate change wasn’t something Rob Crassweller wanted to discuss at a fruit grower’s meeting Wednesday at the Berks County Agricultural Center.

But he offered the group of around 70 fruit growers a glimpse into how climate change could affect fruit growing in the Keystone State.

Crassweller, professor of pomology at Penn State, said time will tell what the impact of climate change will be on tree fruit growing.

“It’s not really a clear picture,” he said.

On the one hand, the growing season will likely get longer, which could be a positive since some growers could take advantage of an earlier market for their fruit.

“We’re going to have a longer season. That could be good,” he said.

On the other hand, a longer season could bring more issues with insects and disease.

Earlier springs could also put fruit in jeopardy if there are sudden bouts of cold air.

In Crassweller’s own orchards in Rock Springs, Pa., the site of one of Penn State’s research farms, his apple production last year went from 3,400 bushels to just 32 bushels because of early bud emergence and subsequent freeze and frost cycles.

“It’s been a recent trend. It’s just interesting the last four years, we’ve had issues with temperatures,” he said.

Crassweller has analyzed apple production data in four states — Michigan, New York, Pennsylvania and Virginia — since 2006. While three of the four have seen fairly consistent production, Michigan, which has some of the coldest temperatures, has seen very erratic production, he said, likely caused by early bud breaks and colder temperatures later.

“They really are the ones that are suffering the most,” he said. “You as a grower can’t consistently make money like that.”

Crassweller said growers could invest in things like wind machines to prevent freeze or frost damage in the spring.

He also thinks there could be less acreage of fruit overall, as growers would likely only grow trees in the best spots to prevent frost damage.

Growers could take advantage of the fact that fruits such as peaches could come off as early as June and there would be more time in the fall to apply herbicides and do some of the things that need to be done to get orchards ready for overwintering.

“We’re not going to be running around to get everything picked,” he said.

For Ben Keim, who grows 75 acres of fruit in Boyertown, Berks County, the changing weather is something he’s already started adjusting to.

“It is something we are focusing on. Primarily what we are concerned with is how we’re adjusting to rainfall as well as temperature,” Keim said.

One thing he’s seen as of late is drier summers, which can affect fruit size and quality. He’s also had to do more irrigation, which costs more money.

“Wind machines can help in early spring; irrigation can provide that protective layer. But it’s not something we have as much control over as say selecting the varieties based upon whether they bloom early, bloom later or being able to add water to the crops,” he said.

Noemi Halbrendt, plant pathologist at the Penn State Fruit Research and Extension Center, said growers should rotate fungicide sprays and focus more on timing to prevent apple scab resistance, which has become an issue the past few seasons.

Apple scab is one of the most serious diseases in apples. The pathogen can be prevalent throughout the growing season, but is worse in cool, humid conditions.

Spraying for apple scab can be especially important during petal fall and soon after, which Halbrendt said is the most critical time for spraying.

Apple scab causes early defoliation and can lead to less productive fruit trees. Halbrendt said scab resistance can appear after just two consecutive sprays of the same fungicide.

The pathogen actually overwinters in dead and infected leaves.

Halbrendt said one way to possibly control pathogen spores is to rake away leaves to reduce the number of spores or apply urea to help spores dissipate, with fall application the most effective

Not controlling spores, she said, could be bad because unique strains can come out of a lot of spores, making the disease even more difficult to control.

Another way to control it is plant apple scab resistant varieties.

Site-specific fungicides, she said, are generally more effective than multipurpose fungicides in controlling disease, but they are also more prone to resistance since they generally have a single mode of action.

She said mixing up the fungicides to not have the same mode of action is something that can be useful.

Also, look at labels and follow what they say.

“It’s an evolutionary process that just occurs,” she said of fungicide resistance. “Once you start using it (fungicide), the clock starts ticking.”